Background and Purpose- Intracranial artery dissection can eventually lead to subarachnoid or intracerebral hemorrhage. Little is known about the clinical features and risks associated with extracranial vertebral artery dissection that extends intracranially. The clinical and imaging characteristics of extracranial vertebral artery dissection (eVAD) with (e+iVAD) or without (eVAD) intracranial extension were analyzed. Methods- The frequency of ischemic events, including ischemic strokes and transient ischemic attacks, was compared between e+iVAD and eVAD patients from a monocentric cohort study. Results- Among 328 patients with cervical artery dissection, vertebral artery dissection was diagnosed in 153 individuals. Twenty-nine patients had e+iVAD (19%) and 124 patients had only eVAD (81%). Cardiovascular risk factors did not differ between these 2 groups, but ischemic events were more frequent in patients with e+iVAD than in patients with eVAD (86% versus 48%, P=0.0002). Subarachnoid hemorrhage occurred in 1 patient with e+iVAD and in 9 with eVAD (6% versus 3%, P=0.53). Intracranial extension was an independent factor associated with ischemic stroke at admission (odds ratio, 6.43; 95% CI, -1.96 to 21.08; P=0.002) after adjustment for cardiovascular risk factors and imaging findings. Conclusions- In a large cohort of patients with vertebral artery dissection, intracranial extension of the vessel dissection appears associated with an increased risk of ischemic stroke.< Réduire